Polyethylene experimental results

KEN Kennis, H.A.J., Loos, Th.W. de, DeSwaan Arons, J., Van der Haegen, R., and Kleintjens, L.A., The influence of nitrogen on the liquid-hquid phase behavioiu of the system n-hexane-polyethylene experimental results and predictions with the mean-field lattice-gas model, (experimental data by Th.W. de Loos), Chem. Eng. Sci., 45, 1875, 1990. 

Fig. 7 gives an example of such a comparison between a number of different polymer simulations and an experiment. The data contain a variety of Monte Carlo simulations employing different models, molecular dynamics simulations, as well as experimental results for polyethylene. Within the error bars this universal analysis of the diffusion constant is independent of the chemical species, be they simple computer models or real chemical materials. Thus, on this level, the simplified models are the most suitable models for investigating polymer materials. (For polymers with side branches or more complicated monomers, the situation is not that clear cut.) It also shows that the so-called entanglement length or entanglement molecular mass Mg is the universal scaling variable which allows one to compare different polymeric melts in order to interpret their viscoelastic behavior. 

Fig. 15. Comparison of the viscosities either directly measured or calculated from the spin-echo results for polyethylene melts at 509 K as a function of molecular mass ( experimental result o viscosities calculated on the basis of mode analysis). (Reprinted with permission from [52]. Copyright 1993 The American Physical Society, Maryland)...

Attempts were made to include all hydrogen atoms explicitly in the simulations. This computationally demanding explicit-atom model shows (Fig. 1) that the crystal symmetry is orthorhombic, in agreement with the well-known experimental result for polyethylene single crystals, instead of the hexagonal symmetry seen in united-atom model simulations. 

The calculations also predict that polysilane should have a higher equilibrium flexibility than polyethylene,178 and solution characterization techniques could be used to test this expectation. Dynamic flexibility can also be estimated from such energy maps, by determining the barriers between energy minima. Relevant experimental results could be obtained by a variety of dynamic techniques.179... 

Sakai and Hashimoto (33) presented experimental results on devolatilization of a mixture of octane/hexane in linear low density polyethylene (LLDPE) from 10% to 0.01%, as well as a rubber slurry of 42% chloroprene and of 58% slurry in carbon tetrachloride in a JSW TEX 65 counterrotating, intermeshing, TSE. The LLDPE mixture was prepared in SSE upstream, where the octane/hexane was added to the melt with a plunger pump, which maintained constant concentration and was fed directly under pressure into the feed throat of the counterrotating, vented, TSE. 

By way of example, the experimental results of Meissner (1971) on low-density polyethylene have been represented in Fig. 15.22, by plotting rie/))eo against t/x0 with as a parameter. For low values of all points lie on a single curve, which shows some correspondence to the curves of Fig. 15.16 for rj/rj0 against yxQ. If e > 1, however, the extensional viscosity increases considerably with increasing extension. 

Figure 5. Theoretical (FSGO) and experimental XPS valence spectra of various fluaro-polyethylenes (theoretical results do not include any cross-section effects)...

The aim of this section is to perform comparisons between the predictions of some constitutive equations and experimental results in simple shear and uniaxial elongation on three polyethylenes. In addition, this is expected to provide well-defined sets of material parameters to be used in the model equations for the computation of complex flows. 

In the case of branched polyethylene the danger that staining may affect the crystal surfaces is considerably increased. However, under very careful staining conditions the experimental results for a large number of different polyethylene co-polymers have been found to be very reproducible and consistent. 

Another application of atomistic simulations is reported by De Pablo, Laso, and Suter. Novel simulations for the calculation of the chemical potential and for the simulation of phase equilibrium in systems of chain molecules are reported. The methods are applied to simulate Henry s constants and solubility of linear alkanes in polyethylene. The results seem to be in good agreement with experiment. At moderate pressures, however, the solubility of an alkane in polyethylene exhibits strong deviations from ideal behavior. Henry s law becomes inapplicable in these cases. Solubility simulations reproduce the experimentally observed saturation of polyethylene by the alkane. For low concentrations of the solute, the simulations reveal the presence of pockets in the polymer in which solubility occurs preferentially. At higher concentrations, the distribution of the solute in the polymer becomes relatively uniform. 

Figures 16 and 17 show some of the important results that Corradini obtained. Figure 16 plots the computed X-ray-diffracted intensity versus (47t sin 9)/. The predicted intensities agree well with the experimental results of molten polyethylene. Figure 17 plots the correlation parameter t versus the distance r, where T(r) is given by...

Experimental results for the static structure factor of polyethylene are given in Figure 19, which shows results from PRISM calculations for compari-The calculations used hard sphere diameters of 3.70 and 3.90 A. The... 

The polyethylene mass flow rate is 1501bm/hr and the melt density is SSlbm/tf thus, the volumetric flow rate is (1501bm/hr)/(55 Ibrn/tf) = 2.73 fC/hr. The experimental results for the inlet and outlet temperature profiles are given in Figure 10.35. Let s determine the blending performance of the mixer from correlations and then relate that to the experimental data. 

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